Sto Failure; Sto Feedback - Danfoss iC7 Series Operating Manual

iC7 Series Functional Safety
Operating Guide
2 ms max. Test pulse
STO Ch. A/B
STO function
Active
Inactive
Illustration 1: Test Pulse Filtering
• Asynchronous input tolerance: The input signals at the STO terminals are not always synchronous. If the discrepancy between
the two signals is longer than 500 ms, the drive indicates a STO fault as described in
activation of the STO function.
STO Ch. A/B
Ch.A
Ch.B
Discrepancy time
STO function
Active
Inactive
Illustration 2: Discrepancy Time

3.5.2 STO Failure

An internal hardware failure might lead to a mode where an external STO request does not lead to the de-energizing of the motor.
The PFH/PFD and MTTF values stated in
other STO-related, internal failures lead directly to an unrequested activation of the STO function, or effect only one of the 2 redun-
dant STO channels. Failures effecting a single channel are detectable when performing the diagnostic test specified in
and Maintenance.

3.5.3 STO Feedback

STO feedback is a single channel feedback signal which can be used for diagnostic purposes, and for providing an indication of an
active STO. It can help to achieve better safety capability on system level, for example, in retrofit cases, where a diagnostic feedback
to the safety system is required.
10 | Danfoss A/S © 2023.03
STO demanded
Time
Debounce time
Time
7.1 Functional Safety Standards and Performance
iC7 Functional Safety
Table 4. This feature does not delay the
reflect the probability of this fault. Any
AQ319741840653en-000201 / 136R0268
6 Operation